This invention relates to orifice plates for fluid ejection devices, and more particularly to methods for manufacturing an orifice plate having a plurality of closed slits.
Ink jet printing mechanisms use pens that shoot droplets of colorant onto a printable surface to generate an image. Such mechanisms may be used in a wide variety of applications, including computer printers, plotters, copiers, and facsimile machines. For convenience, the concepts of the invention are discussed in the context of a printer. An ink jet printer typically includes a print head having a multitude of independently addressable firing units. Each firing unit includes an ink chamber connected to a common ink source via channels in a substrate, to an ink outlet nozzle defined in a thin metal orifice plate common to all nozzles on a print head.
In some configurations, a three color pen has three different channels running parallel to each other and nearly spanning the entire substrate. Print heads are assembled by registering the corresponding rows of orifices with the ink channels in the substrate. The orifice plate is attached to the substrate with a barrier layer that serves as an adhesive gasket to isolate the orifices and ink channels from each other to prevent cross leakage. The adhesion is conducted under pressure and at elevated temperature. Because the metal plate has a greater coefficient of thermal expansion than the silicon substrate, thermal stresses are generated when the print head equilibrates at room temperature. The silicon substrate is normally strong enough to withstand the compressive forces generated by the stress in the print head, except that the ink channels weaken the substrate against forces perpendicular to the channels. With larger sized print head substrate dies, unwanted warpage may occur. When the assembled wafers are sawed apart into separate print head dies, chipping or wafer breakage may occur due to thermal stresses. Some breakage can be avoided by sawing at slower feed rates, but this increases manufacturing time and costs.